2,010 research outputs found
Modelling of thermo-chemical properties over the sub-solidus MgO–FeO binary, as a function of iron spin configuration, composition and temperature
Thermo-chemical properties and T–X phase relations diagram of the (Mg,Fe)O solid solution are modelled using mixing Helmholtz energy, ΔF(T,x)mixing, calculated by quantum mechanical and semi-empirical techniques. The sub-solidus MgO–FeO binary has been explored as a function of composition, with iron either in high-spin (HS) or low-spin (LS) configuration. Only the HS model provides physically sound results at room pressure, yielding a correct trend of cell edge versus composition, whereas LS’s issues are at variance with observations. Mixing Helmholtz energy has been parametrized by the following relationship: ΔF(T,x)mixing = x × y × [U0(T) + U1(T) × (x – y) + U2(T) × (x − y)2]−T × S(x,y)config, where y = 1−x and Uj(T) are polynomials in T of the second order. ΔF(T,x)mixing exhibits a quasi-symmetric behaviour and allows one to build the T–X phase relations diagram over the MgO–FeO join. The HS model including vibrational contribution to the Helmholtz energy predicts a solid solution’s critical temperature of some 950 K, remarkably larger than olivine’s and Mg–Fe garnet’s. All this points to a more difficult Mg–Fe mixing in periclase-like structure than olivine and garnet, which, in turn, provide more structure degrees of freedom for atomic relaxation. From ΔF(T,x)mixing, we have then derived ΔH(T,x)excess and ΔS(T,x)excess. The former, characterized by a quasi-regular behaviour, has been parametrized through W × x × (1−x), obtaining WH,Mg–Fe of 17.7(5) kJ/mol. ΔS(T,x)excess, in turn, increases as a function of temperature, showing absolute figures confined within 0.1 J/mol/K. Mixing Gibbs energy, calculated combining the present issues with earlier theoretical determinations of the magnesio-wüstite’s elastic properties, has shown that the HS configuration is stable and promote Mg–Fe solid solution up to ≈15 GPa
Ab-initio investigation of the thermodynamic stability of the magnesio-w\ufcstite solid solution under Earth\u2019s lower mantle conditions
Fe-periclase reactivity at Earth's lower mantle conditions: Ab-initio geochemical modelling
Intrinsic and extrinsic stability of the (Mg,Fe)O solid mixture in the Fe-Mg-Si-O system at high P, T conditions relevant to
the Earth\u2019s mantle is investigated by the combination of quantum mechanical calculations (Hartree- 26 Fock/DFT hybrid
scheme), cluster expansion techniques and statistical thermodynamics. Iron in the (Mg,Fe)O binary mixture is assumed to
be either in the low spin (LS) or in the high spin (HS) state. Un-mixing at solid state is observed only for the LS condition
in the 23\u201342 GPa pressure range, whereas HS does not give rise to un-mixing. LS (Mg,Fe)O un-mixings are shown to be able
to incorporate iron by subsolidus reactions with a reservoir of a virtual bridgmanite composition, for a maximum total enrichment
of 0.22 FeO. At very high P (up to 130/3150 GPa/K), a predominant (0.7 phase proportion), iron-rich Fe-periclase
mixture (Mg0.50Fe0.50)O is formed, and it coexists, at constrained phase composition conditions, with two iron-poor assemblages
[(Mg0.90Fe0.10)O and (Mg0.825Fe0.175)O]. These theoretical results agree with the compositional variability and frequency
of occurrence observed in lower mantle Fe-periclase from diamond inclusions and from HP-HT synthesis
products. The density difference among the Fe-periclase phases increases up to 10%, between 24 and 130 GPa. The calculated
bulk Fe/Mg partitioning coefficient between the bridgmanite reservoir and Fe-periclase, Kd, is 0.64 at 24 GPa; it then
drops to 0.19 at 80 GPa, and becomes quasi-invariant (0.18\u20130.16) in the lowermost portion of the Earth\u2019s mantle (80\u2013
130 GPa). These Kd-values represent an approximate estimate for the Fe/Mg-partitioning between actual bridgmanite and
Fe-periclase. Consequently, our Kd-values agree with experimental measurements and theoretical determinations, hinting
that iron preferentially dissolves in periclase with respect to all the other iron-bearing phases of the lower mantle. The continuous
change up to 80 GPa (2000 km depth) of the products (compositions and phase proportions) over the MgO-FeO
binary causes geochemical heterogeneities throughout the lower mantle, but it does not give rise to any sharp discontinuity.
In this view, anomalies like the ULVZs, explained with a local and abrupt change of density, do not seem primarily ascribable
to the mixing behavior and reactivity of (Mg,Fe)O at subsolidus
Electromagnetic dipole moments of charged baryons with bent crystals at the LHC
We propose a unique program of measurements of electric and magnetic dipole
moments of charm, beauty and strange charged baryons at the LHC, based on the
phenomenon of spin precession of channeled particles in bent crystals. Studies
of crystal channeling and spin precession of positively- and negatively-charged
particles are presented, along with feasibility studies and expected
sensitivities for the proposed experiment using a layout based on the LHCb
detector.Comment: 19 pages, 13 figure
Dopant profiling on ultra shallow junctions in Si with ADF-STEM
The utmost scaling of the electronic devices nowadays attained, requires both ultra shallow junctions and high levels of dopant concentration and activation. In these conditions, the presence of surfaces or interfaces assumes a very important role in the determination of the dopant distribution during post-implantation annealing. In this work, we show how the Z-contrast annular dark field scanning transmission electron microscopy (ADF-STEM) technique, pionereed by Pennycook and coworkers [1], can be optimised to give reliable dopant profiles at a subnanometer scale thus satisfying some of the new needs of the ultra shallow implants characterization
Glycine Receptor Antibody-Associated Progressive Encephalomyelitis with Rigidity and Myoclonus (PERM) During SARS-CoV-2 Infection: a Video-Case Report
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Investigation of dopant profiles in nanosized materials by scanning transmission electron microscopy
Scanning electron microscopy is capable to provide chemical information on specimens interesting for the field of materials science and nanotechnology. The spatial resolution and the chemical information provided by incoherent imaging and detection of transmitted,
forward-scattered electrons can reveal useful information about the specimen composition and microstructure. This paper discusses the capability and potential of low-voltage Scanning Transmission Electron Microscopy (STEM) for the characterization of multilayered structures and dopant profiles in crystalline materials
Efficient Passive ICS Device Discovery and Identification by MAC Address Correlation
Owing to a growing number of attacks, the assessment of Industrial Control
Systems (ICSs) has gained in importance. An integral part of an assessment is
the creation of a detailed inventory of all connected devices, enabling
vulnerability evaluations. For this purpose, scans of networks are crucial.
Active scanning, which generates irregular traffic, is a method to get an
overview of connected and active devices. Since such additional traffic may
lead to an unexpected behavior of devices, active scanning methods should be
avoided in critical infrastructure networks. In such cases, passive network
monitoring offers an alternative, which is often used in conjunction with
complex deep-packet inspection techniques. There are very few publications on
lightweight passive scanning methodologies for industrial networks. In this
paper, we propose a lightweight passive network monitoring technique using an
efficient Media Access Control (MAC) address-based identification of industrial
devices. Based on an incomplete set of known MAC address to device
associations, the presented method can guess correct device and vendor
information. Proving the feasibility of the method, an implementation is also
introduced and evaluated regarding its efficiency. The feasibility of
predicting a specific device/vendor combination is demonstrated by having
similar devices in the database. In our ICS testbed, we reached a host
discovery rate of 100% at an identification rate of more than 66%,
outperforming the results of existing tools.Comment: http://dx.doi.org/10.14236/ewic/ICS2018.
Great occipital nerve long-acting steroid injections in cluster headache therapy: an observational prospective study
Background: Injections targeting the occipital nerve are used to reduce headache attacks and abort cluster bouts in cluster headache patients. There is no widely accepted agreement over the optimal technique of injection, type and doses of steroids and/or anesthetics to use, as well as injection regimens. The aim of this study was to verify the effectiveness and safety of greater occipital nerve long-acting steroid injections in the management of episodic and chronic cluster headache. Methods: We conducted a prospective observational cohort study on episodic (ECH) and chronic cluster headache patients (CCH). ECH were included in the study at the beginning of a cluster period. Three injections with 60 mg methylprednisolone were performed on alternate days. We registered the frequency and intensity of attacks three days before and 3, 7 and 30 days after the treatment, the latency of cluster relapse, adverse events, scores evaluating anxiety (Zung scale), depression (Beck’s Depression Scale) and quality of life (Disability Assessment Schedule II, 12-Item Self-Administered Version). Primary outcome was the interruption of the cluster after the three injections. Responders conducted a follow-up period of 12 months. Results: We enrolled 60 patients, 47 with ECH and 13 with CCH. We observed a complete response in 47.8% (22/46) of episodic and 33.3% (4/12) of chronic patients. Moreover, a partial response (reduction of at least 50% of attacks) was obtained in further 10.8% (5/46) of episodic and in 33.3% (4/12) of chronic patients at 1 month. Median pain-free period was of 3 months for CCH responders. Only mild adverse events were reported in 38.3% (23/58) cases. Conclusions: We suggest three greater occipital nerve injections of 60 mg methylprednisolone on alternate days as useful therapy in episodic and chronic cluster headache. This leads to a long pain-free period in chronic forms. Adverse effects are mild and support its use as first choice. Trial registration: The study was inserted in AIFA observational studies register
Clinical Management of Long-Term Survivors after Classical Hodgkin Lymphoma and Diffuse Large B-Cell Lymphoma
Compared to other patients suffering from hematological malignancies, classical Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma (DLBCL) patients have a long life expectancy when in complete remission at the end of first, or sometimes second, line treatments [...]
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